import java.util.*;

public class Encoding
{
   public static Set<String> morseCodes(int m, int n)
   {
      Set<String> result = new TreeSet<>();
      if (m == 0 && n ==0){
         result.add(" ");
      }

      else if (m == 1 & n == 0){
         result.add(".");
      }

      else if (m == 0 & n == 1){
         result.add("-");
      }

      else{
         Set<String> subresult1 = morseCodes(m-1, n);
         Set<String> subresult2 = morseCodes(m, n-1);

         for(String str: subresult1){
         }

         for(String str : subresult2){

         }
      }
      return result;
   }
}